Method of arc welding using carbon dioxide as a shielding medium and a deoxidizing metal addition



May 15, 1962 J. J. CHYLE USING EDIUM AND A DEOXI 3,035,153 IELDINGMETHOD OF ARC WELDING CARBON DIOXIDE AS A SH M DIZING METAL ADDITIONOriginal Filed Oct. '7, 1954 FIG. I.

FEED

CONTROL RECTIFIER INVENTOR. John J. C Pzy Ze ana, I A Mb ATTORNEYS.

Patented May 15, 1962 METHOD OF ARC WELDING USING CARBON DIOXIDE AS ASHIELDING MEDIUM AND A DEOXIDHZING METAL ADDITIQN John J. Chyle,Wauwatosa, Wis, assignor to A. 0. Smith gorporation, Milwaukee, Wis., acorporation of New ork Continuation of application Ser. No. 460,943,Oct. 7, 1954. This application Nov. 26, 1956, Ser. No. 624,467

2 Claims. (Cl. 219-74) This invention relates to a method of arc weldingand particularly to an arc welding method wherein the arc is maintainedin an atmosphere of shielding gas.

This is a continuation application of application Serial No. 460,943filed October 7, 1954, of the same inventor, now abandoned.

Arc welding in an atmosphere of a non-oxidizing gas with either aconsumable electrode or a non-consumable electrode is known in thewelding art. An inert gas such as helium, argon or a mixture of the twohas been extensively employed. When a consumable electrode is employed,the work and electrode are generally connected with reverse polarity,i.e. the work is connected to the negative side of the welding currentsource and the electrode is connected to the positive side of thewelding current source. The above arrangement permits an extremely rapidfeed of the electrode toward the work. Although the above method ofwelding provides sound welds, helium and argon are relatively scarce andare expensive gases.

It has been suggested in the prior art to use a less costly gas such ascarbon dioxide as a shielding medium, but attempts to employ carbondioxide have not met with success. For example, the patent to AlexanderNo. 1,746,207 speaks of welding in an atmosphere of carbon dioxide andconcludes that in every case the welds were brittle and not as good aswelds made in air. Similarly the the paper Studies on Electric Weldingby Ludwig J. Weber from the Transactions of the American Society forSteel Treating presented September 20, 1926, discloses that welds madein a carbon dioxide atmosphere are not satisfactory due to the oxidationof the iron.

The patents to Lincoln No. 1,589,017 and No. 1,711,151 disclose the useof an inert gas, such as carbon dioxide or nitrogen, with a lowamperage,-non-consumable carbon electrode system, but this method hasnever proven successful in commercial practice.

In some cases small amounts of carbon dioxide have been used incombination with other gases, such as argon, helium or car-bon monoxide,to provide a gaseous shield that produced favorable results. In thiscombination of gases there is again the problem of using the relativelyscarce and expensive gases argon and helium. The use of carbon dioxidealone is desirable because of the generally low cost and availability ofcarbon dioxide. However, the use of carbon dioxide alone as a shieldinggas has never provided acceptable results.

The copending application of the applicant, Serial No. 460,944, filedOctober 7, 1954 and entitled, Method of Arc Welding Using Carbon Dioxideas a Shielding Medium is based on the discovery that sound welds can beproduced with a shielding gas consisting solely of carbon dioxide whenusing a killed steel consumable electrode and by controlling the speedof the electrode feed and the current density within predeterminedlimits. The present invention goes a step beyond that invention andprovides a further improvement in welding with a carbon dioxide gasshield by using a steel electrode having appreciable amounts of adeoxidizing metal combined therewith.

According to the invention the steel weld rod is coated or alloyed witha deoxidizing metal such as aluminum, silicon, titanium, magnesium,zirconium or manganese in an amount such that the deoxidizing metalcomprises from 0.20% to 3.0% by weight of the total weight of the steelrod and the added metal. The steel electrode with the metal addition isfed toward the workpiece at a speed in the range of 200 to 600 inchesper minute and the current density is maintained at a value of over85,000 amperes per square inch.

With the high rate of electrode feed and the high current densitycombined with the deoxidizing metal additions to the electrode, it ispossible to produce sound uniform welds.

The drawing furnished herewith illustrates the best mode presentlycontemplated for carrying out the invention.

FIGURE 1 is a schematic arrangement adapted for arc welding inaccordance with the present invention; and

FIG. 2 is an enlarged transverse section of the electrode.

Referring to the drawing, there is shown a workpiece 1 to be welded bystriking an are between the workpiece 1 and a consumable steel electrode2 which may be in wire or rod shape. As shown in the drawing, reversepolarity arc welding is employed with the workpiece 1 connected to thenegative terminal 3 of a source of direct current shown as a rectifier 4and the electrode 2 connected to positive terminal 5 of the rectifier 4.The connection of the electrode 2 to the electric circuit is by asliding contact 6 to allow movement of the consumable electrode. As thewelding progresses, the portion of the electrode adjacent the workpieceis burned off and transferred to the workpiece 1.

To maintain a predetermined arc length between the electrode and thework, the electrode 2 is continuously drawn from a reel 7 by feedrollers 8 and fed through a welding head 9 toward the workpiece 1. Thefeed rollers 8 are variably driven by a motor 10* in accordance with thearc length as hereinafter described. The arc length is maintainedpractically constant by connecting the arc voltage as a voltage sourceto an electrode feed control 11 connected to the feed motor 10. If thearc voltage fluctuates, the feed control 11 varies the speed of the feedmotor to return the arc length to normal. For example, if the arc lengthincreases above normal, the arc voltage increases and this increasedvoltage is applied to the feed motor so as to increase the feed of theelectrode 2 to the work. Conversely, a decrease in arc length andtherefore are voltage results in a reduction of the feed of electrode 3and a lengthening of the arc length until a normal arc is obtained. Thisis a conventional variable electrode feed arrangement and the feedcontrol 11 is therefore shown in diagrammatic form.

The welding head 9 is constructed with concentric cylinders 12 and 13with the Wire electrode 2 passing through the central cylinder 12. Thetop of the outer cylinder 13 is sealed to the inner cylinder 12 by a cap14 welded to the outer surface of the cylinder 12 and is threaded ontothe outer cylinder 13 to provide an annular passage 15 between thecylinders 12 and 13. To introduce carbon dioxide about the welding are,a source 16 of carbon dioxide is connected to the passage 15 by a tube17. A valve 18 in the tube 17 is employed to regulate the fiow of gas tothe passage 15. The carbon dioxide passes through passage 15 and isdischarged concentrically of the electrode to envelop the arc andthereby protect the welding zone from the surrounding atmosphere.

The electrode 2 of the present invention is composed of about 0.20% to3.0% of a deoxidizing metal and the balance being steel. The deoxidizingmetal may be in the form of a thin coating 19 on a steel core, as shownin FIG. 2 or a coating of finely divided particles bonded to a steelcore, or the electrode itself may be an alloy of steel and thedeoxidizing metal in the above proportions.

The deoxidizing metal is a metal having a strong affinity for oxygen andnitrogen and serves to convert any oxygen formed by the decomposition ofcarbon dioxide into a stable compound.

The deoxidizing metal also converts any iron oxide present in the moltenweld metal to a more stable compound and thereby produces sounder welds.The metal may consists of aluminum, silicon, titanium, magnesium,zirconium, manganese or the like. It is desired that the amount of themetal be in excess of the amount usually found in a steel killed withthat particular metal.

In order to obtain a uniform metal transfer from the electrode 2 to theworkpiece a high current density is employed. Generally, the lower limitof the current density should be that minimum amount which will producea uniform metal transfer and the upperlimit of the current densityshould be that maximum amount which can be put into the electrode 2without exploding the rod. More specifically, the current density shouldbe at least 85,000 amperes per square inch, and for usual operations acurrent density of 100,000 to 200,000 amperes per square inch has provenvery satisfactory.

In combination with the high current density, the speed of the electrodefeed toward the workpiece should be in the range of 200 to 600 inchesper minute. A feed of about 375 inches per minute has proven verysatisfactory. The rate of electrode feed will normally result in travelof the welding head along the seam to be welded at about 8 to 150 inchesper minute depending on the nature of the articles to be welded.

The rate of flow of carbon dioxide should be sufiicient to continuallypurge the atmosphere at the region surrounding the arc. For mostoperations and electrode diameters the flow of carbon idoxide should bebetween 15 to 50 cubic feet per hour, and generally a rate of flowbetween 20 and 35 cubic feet per hour, is most satisfactory. This rateof flow of carbon dioxide is substantially less than the rate of flow ofargon or helium which would be necessary with a corresponding electrodefeed and Welding amperage.

It has been found that the rate of flow of carbon dioxide should bemaintained below a certain level on the nozzle opening, or the pressureregulator may freeze. If the rate of flow of the carbon dioxide ismaintained below 50 cubic feet per hour this danger will ordinarily beeliminated.

A typical example of the use of the present invention as applied to thewelding of an automotive control arm is as follows:

Stock compositionA. O. Smith Corp. spec. 1056:

Carbon 0.180.25%.

Manganese 0.300.60%.

Phosphorus 0.04% maximum.

Sulphur 0.05% maximum.

Copper 0.20% maximum.

Iron Balance. Type of weld Circular groove, filet weld. Electrode sizeinch diameter.

Electrode composition:

Carbon 0.17%. Manganese 1.10%. Phosphorus 0.012%. Sulphur 0.027%.Silicon 0.20%. Iron Balance. Thickness of aluminum 0.005 inch.

Speed of electrode feed 210 inches/minute.

Speed of arc travel 19.3 inches/minute. Arc voltage 30 volts. Arcamperage 300 amperes. Current density 100,000 amperes/ square inch. Rateof flow of CO 20 cubic feet/hour.

This procedure resulted in a sound uniform weld, free of porosity, andother physical defects.

While the above description is directed to the use of reverse polarityin the welding operation, it is contemplated that under certainconditions straight polarity can also be employed. For example, if it isdesirable to have a smooth action with minimum spatter then reversepolarity should be used, but if spatter is not objectionable, thenregular polarity can also be used.

Similarly, the use of direct current is not essential. In some instancesit may be desirable to employ alternating current and the resultsobtainable with alternating current are acceptable.

The present invention provides a method obtaining more effective weldswith the use of carbon dioxide gas as a shielding medium in arc welding.The properties of the welds are improved by using metal additions of adeoxidizing metal with a consumable steel electrode and employing ahighrate of electrode feed and a high current density during the weldingoperation.

Various modes of carrying out the invention are contemplated as withinthe scope of the following claims particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

I claim:

1. A method of arc welding, comprising establishing an are between aconsumable steel electrode and a workpiece, said electrode consisting byweight of 0.20% to 3% of a strongly deoxidizing metal and the balanceiron, feeding a gaseous medium consisting of substantially pure carbondioxide to the are at a rate of 15 to 50 cubic feet per hour to form agaseous envelope around the arc and thereby exclude the surroundingatmosphere from the are, feeding the electrode toward the workpiece at aspeed of 200 to 600 inches per minute while maintaining a currentdensity in said electrode of above 85,000 amperes per square inch, andthe deoxidizing metal in the electrode converting any oxygen formed bythe decomposition of the carbon dioxide into a stable compoundnondeleterious to the weld formed by said method.

2. A method of arc welding comprising establishing an are between aworkpiece and a consumable steel electrode containing 0.20% to 3.0% of adeoxidizing metal selected from the group consisting of aluminum,silicon, titanium, zirconium and magnesium, feeding substantially purecarbon dioxide to the arc to form a gaseous envelope around the arc andthereby exclude the surrounding atmosphere from the arc, and feeding theelectrode toward the workpiece at a speed of 200 to 600 inches perminute while maintaining a current density in the electrode of 100,000to 200,000 amperes per square inch, said deoxidizing metal in theelectrode converting any oxygen formed by the decomposition of thecarbon dioxide into a stable compound.

References Cited in the file of this patent UNITED STATES PATENTS2,504,867 Muller Apr. 18, 1950 2,504,868 Muller et a1 Apr. 18, 19502,544,711 Mikhalapov Mar. 13, 1951 2,824,948 Willigen et a1 Feb. 25,1958 FOREIGN PATENTS 736,241 Great Britain Sept. 7, 1955 1,094,722France Dec. 8, 1954 1,102,303 France May 4, 1955 UNITED STATES PATENTOFFICE CERTIFICATE OF CORRECTION Patent No 3,035,153 May 15,. 1962 JohnJ. Chyle in the above numbered pet- It is hereby certified that errorappears ers Patent should read as ent requiring correction and that thesaid Lett corrected below.

"idoxide" read dioxide line 72,

Column 3, line 38, for

kness of aluminum coating for "Thickness of aluminum" read Thic Signedand sealed this 20th day of November 1962.

(SEAL) Attest:

DAVID L. LADD Attesting Officer

1. A METHOD OF ARC WELDING, COMPRISING ESTABLISHING AN ARC BETWEEN ACONSUMABLE STEEL ELECTRODE AND A WORKPIECE, SAID ELECTRODE CONSISTING BYWEIGHT OF 0.20% TO 3% OF A STRONGLY DEOXIDIZING METAL AND THE BALANCEIRON, FEEDING A GASEOUS MEDIUM CONSISTING OF SUBSTANTIALLY PURE CARBONDIOXIDE TO THE ARC AT A RATE OF 15 TO 50 CUBIC FEET PER HOUR TO FORM AGASEOUS ELVELOPE AROUND THE ARC AND THEREBY EXCLUDE THE SURROUNDINGATMOSPHERE FROM THE ARC, FEEDING THE ELECTRODE TOWARD THE WORKPIECE AT ASPEED OF 200 TO 600 INCHES PER MINUTE WHILE MAINTAINING A CURRENTDENSITY IN SAID ELECTRODE OF ABOVE 85,000 AMPERES PER SQUARE INCH, ANDTHE DEOXIDIZING METAL IN THE ELECTRODE CONVERTING ANY OXYGEN FORMED BYTHE DECOMPOSITION OF THE CARBON DIOXIDE INTO A STABLE COMPOUNDNONDELETERIOUS TO THE WELD FORMED BY SAID METHOD.